Abstract
Background: Despite significant pharmacological developments in antiemetic therapy, 60% of people undergoing chemotherapy continue to experience nausea and40% experience vomiting. Poor compliance, drug interactions, and side effects of antiemetic medications are significant contributors to the high prevalence of chemotherapy-induced nausea and vomiting (CINV). Complementary and alternative medicines (CAM), including dietary modifications and nutraceuticals such as ginger, are of growing interest as an adjuvant therapy in the prevention and management of CINV. However, the extant evidence on the dietary and nutraceutical management of CINV is limited.Aim: To address research gaps and limitations in existing evidence by exploring novel interventions, mechanisms of action, and clinical considerations for the dietary management of CINV, with a focus on ginger (Zingiber officinale).
Methods and Results: In seven chapters, nine research questions were answered in nine published research studies: three systematic literature reviews, two randomised controlled trials, one qualitative study, one international evidence-based guideline, one editorial, and one narrative review. Chapter 1 provided an overview of extant literature and rationale for each of the studies described within the thesis. Chapter 2 investigated the dietary strategies for CINV; the systematic review and evidence-based guidelines found some evidence for dietary counselling and follow-up on basic nutrition advice and education delivered by health professionals with nutrition knowledge, and strongest evidence for the use of ginger as a nutraceutical. Chapter 3 explored CAM use (encompassing dietary strategies and nutraceuticals) in people with cancer. The qualitative study found that people undergoing chemotherapy valued CAM as a natural complement to their cancer treatment, providing them with hope for improved wellbeing, with use most strongly influenced by past experiences rather than expert opinion, suggesting health professional support could be improved. The invited editorial in Chapter 3 discussed how improved support for safe and effective CAM use during cancer requires clinical resources, integrated models-of-care, clinical and economic research, and policy that supports funding for health equity and value-based care. Chapter 4 presented a systematic umbrella review on the therapeutic effects of ginger, a CAM often used in people with cancer. The strongest evidence was found for the antiemetic effects of ginger in pregnant women, analgesic effects for osteoarthritis, and glycemic control in type 2 diabetes. Ginger also appeared safe and had a positive effect on blood pressure, weight management, dysmenorrhea, post operative nausea, chemotherapy-induced vomiting, blood lipid profile, and anti inflammatory and antioxidant biomarkers. Chapter 5 presented a systematic review and meta-analysis and randomized placebo-controlled trial on the efficacy of ginger for CINV and related outcomes. Strongest evidence was found for ginger supplementation improving delayed CINV (i.e., delayed nausea incidence and severity, delayed vomiting incidence and frequency) and CINV-related quality of life. Emerging evidence supports the use of ginger for cancer-related fatigue, for which there are minimal treatment options. Some evidence was found for improved health-related quality of life and nutrition status with ginger supplementation and no serious adverse events were reported. Chapter 6 described a narrative review and randomised placebo-controlled pilot trial in humans investigating the effects of ginger supplementation on gastrointestinal bacteria using 16S rRNA sequencing. The narrative review concluded that the mechanisms of action of ginger in animal and cell studies support the anti-inflammatory, analgesic, anti-hypertensive, hypoglycaemic, anti-nausea, blood lipid regulating, and weight management effects of ginger in humans. The randomised controlled trial found that ginger had a positive effect on abundance of health-promoting gastrointestinal bacteria and symptoms of indigestion, proposing a novel mechanism of action of ginger. Chapter 7 discussed the thesis conclusions and recommendations for future practice and research.
Conclusions: The cumulative results presented in this thesis contribute to the extant evidence on the adjuvant dietary and nutraceutical management of CINV advancing our understanding of the mechanisms of action of ginger. This thesis provides rationale for future rigorous clinical trials investigating gastrointestinal microbiota mediated mechanisms and how to best integrate the use of CAM, like ginger, into conventional medicine.
| Date of Award | 8 Jun 2023 |
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| Original language | English |
| Supervisor | Anna Lohning (Supervisor), Skye Marshall (Supervisor), Elizabeth Isenring (Supervisor) & Wolfgang Marx (Supervisor) |